Conventional surface protective layers and interlayer insulating layers for a semiconductor device can include a polyimide resin, which can have excellent heat resistance, electrical characteristics, mechanical properties, and the like. Recently, a photosensitive polyimide precursor composition which can be coated easily has been used to form the polyimide resin. The photosensitive polyimide precursor composition can be coated on a semiconductor device, patterned by ultraviolet (UV) rays, developed, and heat imidized, to easily provide a surface protective layer, an interlayer insulating layer, and the like. Accordingly, it is possible to significantly shorten processing times as compared to conventional non-photosensitive polyimide precursor compositions.
The photosensitive polyimide precursor composition can be a positive type in which an exposed part is dissolved by development, or a negative type in which the exposed part is cured and maintained. Positive type photosensitive resin compositions can be developed by a non-toxic alkali aqueous solution.
An exemplary positive photosensitive polyimide precursor composition includes a polyimide precursor of polyamic acid, a photosensitive material of diazonaphthoquinone, and the like. However, the positive photosensitive polyimide precursor composition may not provide a desired pattern because the carboxylic acid of the polyamic acid can be too highly soluble in an alkali.
In order to solve this problem, a material in which a phenolic hydroxyl group has been introduced instead of carboxylic acid by esterificating polyamidic acid with an alcohol compound having at least one hydroxyl group has been suggested. This material, however, may be insufficiently developed, which can cause problems of film loss or resin delamination from the substrate.
Recently, a material in which a polybenzoxazole precursor is mixed with a diazonaphthoquinone compound has drawn attention. When the polybenzoxazole precursor composition is actually used, however, film loss of an unexposed part may significantly increase, which can make it difficult to obtain a desirable pattern after the developing process. In order to improve this, if the molecular weight of the polybenzoxazole precursor is increased, the film loss amount of the unexposed part may be reduced, but development residue (scum) can be generated, which can decrease resolution and increase development times for the exposed part.
In order to solve the problem, it has been reported that the film loss can be suppressed in non-exposed parts during development by adding a specific phenol compound to a polybenzoxazole precursor composition. However, the effect of suppressing the film loss of the unexposed part can be insufficient. Accordingly, there is still a need for a composition which can sufficiently suppress film loss and prevent the generation of development residue (scum).
A photosensitive resin composition including a novolac resin widely used as a resin for a photoresist, a polyimide precursor or a polybenzoxazole precursor, and a quinone diazide compound has been proposed to improve sensitivity and curing at a low temperature. However, since this composition has deteriorated mechanical properties and storage stability after the thermal curing, it is not useful for forming an insulation layer or a protective layer for a semiconductor device.
Examples of reported solutions to the foregoing problem include the addition of various additives to the composition and the use of a precursor compound that can cross-link and polymerize during the thermal curing. However, while such compositions may improve mechanical properties such as elongation, they lack optical properties such as sensitivity, resolution, and the like. Therefore, there continues to be a need for a composition which can exhibit excellent mechanical properties without deteriorated optical properties.